This invention generally relates to positioning mechanisms; and more specifically, to a mechanism for moving a platform in two orthogonal directions with a high degree of precision.
Some industrial applications require that a workpiece be moved along two orthogonal directions with a very high degree of precision. For example, in the fabrication of integrated circuits, a wafer may be moved through a series of different positions, at each of which a multitude of operations are performed on the wafer. It is important that each operation be performed on a specific, often extremely small, area of the wafer; and to ensure that this is done, the wafer must be located precisely in each of its series of positions. In addition, operations may be performed on the wafer as it is being moved, for instance lithographic exposure, to score a line on the wafer or to deposit or remove material over a predetermined, often very narrow path or line on the wafer. To accomplish this, it is important that the wafer itself be moved with a very high degree of accuracy along a predetermined path.
Various prior art devices are known to move a workpiece with a high degree of precision. Typically, these prior art devices employ complicated mechanical systems involving a large number of machine components, bearings, guideways and lead screws to move the workpiece as desired. These complicated mechanical systems are comparatively expensive and, moreover, as the mechanical elements of the systems wear with use, the precision of the systems decrease.